In recent years, as a solid-state image-capture element such as a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor and the like has been made to have a high resolution, demands for an information device having an imaging function such as a digital still camera, a digital video camera, a mobile phone, a PDA (Personal Digital Assistant) and the like sharply increase. In the meantime, the information device having the image-capture function is referred as an imaging device.
Incidentally, regarding a focus control method of detecting a distance to a main subject and focusing on the subject, there are a contrast AF method and a phase difference AF (Auto Focus). Since the phase difference AF method can detect a focus position at higher speed and with higher precision, compared to the contrast AF method, it is adopted in various imaging devices (for example, refer to Patent Document 1).
FIG. 15 is a plan pictorial view of a general sensor that is used in the phase difference AF method.
The sensor shown in FIG. 15 has a first line on which pixels G1 having an optical opening a eccentric leftwards are arranged in a row direction and a second line on which pixels G2 having an optical opening a eccentric rightwards are arranged in the row direction.
In the sensor shown in FIG. 15, a case is considered in which a black line c extending in a vertical direction is put on pixels of 2 lines×4 columns in the middle and the black line c is in focus, as shown in FIG. 16. It is assumed that an output signal of the pixel covered by the black line c is “0” and an output signal of the pixel not covered by the black line c is “1”. A graph that is formed by plotting the output signals of the pixels at the respective column positions is shown at the lower of FIG. 16. As shown in the graph, it is determined that a signal waveform of the pixels G1 and a signal waveform of the pixels G2 are completely matched and there is no phase difference. Like this, the sensor shown in FIG. 15 can correctly calculate phase difference information for the black line c extending in the vertical direction.
However, in the sensor shown in FIG. 15, when a black line d obliquely extending is put on, as shown in FIG. 17, false detection that there is a phase difference between the signal waveform of the pixels G1 and the signal waveform of the pixels G2 is made even though the black line d is in focus.
It is assumed that an output signal of the pixel of which the opening a is covered by the black line d is “0” and an output signal of the pixel of which the opening a is not covered by the black line d is “1”. A graph that is formed by plotting the output signals of the pixels at the respective column positions is shown at the lower of FIG. 17. As shown in the graph, a deviation occurs between a signal waveform (the dashed-dotted line) of the pixels G1 and a signal waveform (the solid line) of the pixels G2. For this reason, it is determined that there is a phase difference, even though the black line d is in focus. Like this, the sensor shown in FIG. 15 may falsely detect the phase difference information for the black line d extending in the oblique direction.
Patent Document 1: Japanese Patent Application Publication No.: 2011-128302A
The invention has been made keeping in mind the above situations, and an object of the invention is to provide a solid-state image-capture element capable of maintaining phase difference detection precision, irrespective of a direction along which an edge of a subject extends, an imaging device having the same and a focus control method of the imaging device.